Fifteen seconds later Derek solved the mystery, for, approaching the British biplane, was a small monoplane of unmistakably Hun construction—one of the admitted failures of the German Air Service.
The Hun hesitated, banking and circling as if doubtful whether to meet the British craft or to seek safety in flight, while Kaye, all out, bore down to the attack.
"Kaye'll mop him up in a brace of shakes," declared Derek, as he too swung round. "I'll stand by and see the scrap."
Then, seized by an inspiration, he added, "Supposing Fritz has a card up his sleeve?"
Just then the German spun round on one wingtip and began to fly from his antagonist. Kaye's biplane was then about four hundred yards away from, and considerably higher than, the monoplane, and manoeuvring in order to pump a trayful of ammunition into the other's tail.
"Juggins!" ejaculated Derek; "he's let himself into a pretty hole. Properly tricked."
For out of a rift in the clouds, through which the brilliant sunshine poured dazzlingly, three large Hun triplanes swooped. It was an old trick, but Kaye looked like falling a victim to the ruse. His whole attention centred upon the monoplane, which was merely a decoy, he was quite ignorant of the presence of three machines that were waiting to pounce down upon the swallower of the aerial bait.
Derek began to climb, at the same time changing direction in an attempt to intercept the trio of Huns. Without a doubt they had spotted him, but contemptuous of the almost insignificant EG 19 they held on, with the evident intention of first strafing the pursuer of the decoy, and then "mopping up" the second British machine.
Suddenly the decoy, finding that Kaye was perilously close to his tail-plane, dived vertically. Kaye promptly followed suit, while the triplanes, owing to their dead-weight, hesitated to imitate the dangerous stunt.
For a good two thousand feet the Hun monoplane dropped like a plummet, with its engine all out and a long trail of vapour from its noisy exhaust. Then the Hun began a loop that finished him. Making too sharp a curve, the monoplane burst two of the most important tension-wires, and the next instant the wings folded like those of a resting butterfly.